The Icelandic Cancer Society has run a population based cancer registry for the whole nation for 20 years with the objectives of epidemiological research in neoplasia. Such reasearch includes investigation of familiality of neoplastic diseases. The main objective of the Genetics Committee of the University of Iceland is to carry out studies in genetics of the Icelandic population. Such studies include investigations of the possible inheritance of neoplastic diseases. The main demographic files existing in Iceland are the following: Yearly National Roster since 1952, Census December 1 at 5 or 10 year intervals since 1835. The earliest complete census is from 1703. The Parish Books detail vital events. From these and the censuses, complete genealogies can be constructed. Special records exist of all births, marriages and deaths since 1916. Of the above, the National Rosters, the census of 1910 and the records of births, marriages and deaths have already been prepared for mechanical data handling. This application is to extend the coverage of the computerized system for the period back to 1840, and to develop a resource for research into genetics of diseases and other conditions of importance to human health. The genealogical files which at present are computerized, and cover persons alive on 1st December 1910 or born since, are powerful enough to deal with occurrences of moderate frequency, i.e., familiality of breast cancer (see Annex I through V). Such extention would increase the accuracy and the yield of the presently computerized system. The funds requested are to be used to put the genealogical records for 1840-1910 in a form suitable for mechanical family linkage studies of diseases, such as neoplastic.